Fructo-oligosaccharide production from inulin through partial citric or phosphoric acid hydrolyses.

Purified inulin from Dahlia tubers was partially hydrolyzed to form fructo-oligosaccharides by using citric or phosphoric acids (pH, 2.0-2.5) as mild acid catalysts. The ideal kinetic conditions to ensure a high yield of fructo-oligosaccharides relative to free fructose were a temperature range of 85°C-95°C, a hydrolysis time of 15-25 minutes, and a catalyst pH of 2.5. At the higher temperature and the longest hydrolysis time, an inversion of the product ratio occurred. Under these conditions, co-generation of hydroxymethylfurfural occurred, and it was eliminated by activated charcoal. Unlike in classic hydrolysis with hydrochloric or sulfuric acid, deionization of the actual hydrolysates was not necessary because the catalyst neutralization with common bases results in the formation of co-nutrients with alternative uses as foods or fermentation substrates. These whole hydrolysates can be advantageously added as nutraceuticals to carbonated beverages and acidic foods, such as soft drinks and yogurts.

Renal phospholipid metabolism in streptozotocin-induced diabetic rats.

The effect of acute and chronic streptozotocin-induced diabetes on phospholipid metabolism in papillary, medullary and cortical slices was studied. No changes were observed in either the phospholipid content or composition in the papilla, medulla and cortex from acute and chronic diabetic rats. With reference to (U-14C)glycerol incorporation in the papilla from chronic diabetic rats, it increased in PtdCho, PtdIns and PtdEtn. In the medulla, the incorporation to PtdCho decreased in the acute diabetic state, while in the chronic diabetic state the incorporation to PtdCho and PtdIns decreased. No changes were observed in cortical phospholipids from diabetic rats. As regards 23P-sodium orthophosphate incorporation to phospholipids, while it increased in PtdCho, PtdIns and PtdEtn in the papilla from acute and chronic diabetic rats, in the medulla from both groups, the incorporation in PtdCho and PtdIns decreased, and in the cortex from acute diabetic rats it decreased only in PtdIns. Even though no changes were detected in phospholipid composition, alterations in phospholipid metabolism were induced by experimental diabetes.

The enzymes forming isopentenyl pyrophosphate from 5-phosphomevalonate (mevalonate 5-phosphate) in the latex of Hevea brasiliensis.

1. Phosphomevalonate kinase and 5-pyrophosphomevalonate decarboxylase have been purified from the freeze-dried latex serum of the commercial rubber tree Hevea brasiliensis. 2. The phosphomevalonate kinase was acid- and heat-labile and required the presence of a thiol to maintain activity. 3. The 5-pyrophosphomevalonate decarboxylase was relatively acid-stable and more heat-stable than the phosphokinase. 4. Maximum activity of the phosphokinase was achieved at pH 7.2 with 0.2mm-5-phosphomevalonate (K(m) 0.042mm), 2.0mm-ATP (K(m) 0.19mm) and 8mm-Mg(2+) at 40 degrees C. The apparent activation energy was 14.8kcal/mol. 5. Maximum activity of 5-pyrophosphomevalonate decarboxylase was achieved at pH5.5-6.5 with 0.1mm-5-pyrophosphomevalonate (K(m) 0.004mm), 1.5mm-ATP (K(m) 0.12mm) and 2mm-Mg(2+). The apparent activation energy was 13.7kcal/mol. The enzyme was somewhat sensitive to inhibition by its products, isopentenyl pyrophosphate and ADP.